A clinical trial with random assignment to limited radiotherapy fields (involved field, IF) or extended fields (extended field, EF) was begun in 1967 and case accession completed in 1973, with 460 eligible patients assigned to IF, 220, and EF, 240. A total of 95 deaths have been reported, 51 IF and 44 EF, and the remaining 169 IF and 196 EF surviving patients are being followed with the aims (1) of obtaining outcome data through 10 years from enrollment and (2) of obtaining outcome data through 8 years from early extension of disease. Outcome is measured in terms of survival, survival free of extension, complications of therapy, number of extensions, and therapy used in follow-up. The prinicipal comparison is that of the IF and EF regimens, for the total enrolled population and for subgroups defined in terms of initial characteristics of age, sex, stage of disease, symptomatology, histologic type, use of laparotomy in staging, and use of abdominal radiotherapy fields. Secondary comparisons are made to estimate the prognostic significance of the above initial characteristics on survival and the significance of early extension, extranodal extension, and transdiaphragmatic extension to survival.